1. Field of the Invention
The present invention relates to a material to reduce line spaces and hole diameters in resist patterns, a method of forming finely separated patterns with the aid of the material, a method of producing semiconductor devices with the finely separated patterns, and a semiconductor device produced by the method.
2. Background Art
The increasing degree of integration for semiconductor devices needs lines and separations much more fine than before in their manufacturing method. Fine patterns in semiconductor devices are usually formed by resist patterning (photolithography) and ensuring etching on underlying thin layers through the patterned resist as a mask. Therefore, photolithography plays an important role in fine patterning. It consists of steps of resist coating, mask alignment, exposure, and development. The disadvantage of photolithography is that the extent of fineness is limited by the wavelength of light used for exposure. Moreover, in conventional photolithography, it is difficult to control the etching resistance of the resist and hence it is difficult to obtain a desired surface state (such as the surface roughness of the pattern side wall) after etching by controlling the etching resistance.
As mentioned above, the resist pattern formed by photolithography (consisting of resist coating, exposure, and development) has been used as such for the fine patterning of semiconductor devices. The patterns formed in this way are limited in fineness according to the resist performance, the wavelength of light for exposure, and the condition of illumination for exposure. There has been no idea of xe2x80x9cthickeningxe2x80x9d the patterns, thereby making line spaces smaller. Thus, the originally formed resist pattern determines the fineness of the pattern formed on the semiconductor substrate.
In order to solve the above-mentioned problems involved in the prior art technology, the present inventors previously developed a new technology as disclosed in Japanese Patent Laid-open No. Hei 10-73927.
According to this disclosed technology, a first resist pattern is formed by the conventional method. Then, this resist pattern is coated with another resist, which is subsequently crosslinked and developed so as to give a crosslinked film. This crosslinked film sticks to the surface of the first resist pattern, thereby reducing the space between patterned lines and the size of patterned hole opening. In this way it is possible to form the fine patterns which cannot be obtained by using the first resist pattern alone.
The present invention is intended to improve the present inventors""previous technology mentioned above. Therefore, it is an object of the present invention to provide an improved method of forming fine patterns and an improved method of producing semiconductor devices, in which, even when used in a method in which high step differences are produced like isolated residual patterns, a resist is formed so as not to be unevenly coated due to the isolated pattern, and a resist is formed not to cause insufficient thickened pattern and pattern defects.
According to one aspect of the present invention, in a method of manufacturing a semiconductor device, a first resist pattern, which evolves an acid, is formed on a semiconductor substrate. The first resist pattern is treated with a chemical solution containing a crosslinking agent and a swelling promoter, and the crosslinking agent brings about crosslinking in the presence of an acid in the surface layer of the first resist pattern. The crosslinking agent and swelling promoter in the chemical solution is caused to permeate into the surface layer of the first resist pattern, thereby the surface layer is swelled. The chemical solution is removed from the surface of the first resist pattern. The first resist pattern is caused to evolve an acid, and a crosslinked film is formed in the swollen surface layer of the first resist pattern, thereby a second resist pattern is formed. Further, the semiconductor substrate is etched through the second resist pattern as a mask.
In another aspect of the present invention, a chemical solution, for forming a fine pattern, is provided which comprises a solvent, a crosslinking agent, and a swelling promoter. The chemical solution causes the crosslinking agent and swelling promoter to permeate into a resist film, and the crosslinking agent brings about crosslinking in the resist film in the presence of an acid.
Other and further objects, features and advantages of the invention will appear more fully from the following description.